1. Field of the Invention
The present invention relates to a manufacturing method of a porous insulating film by use of a laser, and a manufacturing method of a semiconductor device having a wiring board and a semiconductor element by use of a droplet discharge method typified by an ink jet printing method.
2. Description of the Related Art
In recent years, the thickness of a film constituting each part of a semiconductor element has been reduced for high integration of LSI (Large Scale Integrated circuit), and thus signal delay between multilayers has interfered with high speed operation. Since the signal delay depends on wire resistance and wire capacitance, a higher performance LSI requires a wiring material with a lower resistance and an interlayer insulating film material with a lower dielectric constant.
In order to reduce the resistance of a wire, a copper (Cu) wire having a lower resistance has been properly studied instead of a conventional aluminum (Al) wire, and a wiring process has been performed by a Cu damascene method instead of a conventional Al gap fill method. In the Cu damascene method, a CMP (Chemical Mechanical Polishing) process is used, where excess Cu formed over a Cu wire is polished and removed by use of slurry and a pad while applying load to a substrate.
Meanwhile, in order to reduce wire capacitance, an organic material and an inorganic material that have a lower dielectric constant have been actively proposed and studied instead of a conventional silicon oxide (SiO2) film. Low polarizability and density are considered to be necessary for reduction in relative dielectric constant of an interlayer insulating film.
An organic material has a lower polarizability per unit volume than a silicon oxide film; therefore, it has a lower relative dielectric constant. It is thus suggested that an organic material or a hybrid material of siloxane and an organic molecule is used to reduce the relative dielectric constant of an interlayer insulating film. It is also suggested that perfluorocarbon polymer having a C—F bond (such as poly-tetrafluoroethylene) is used to reduce the relative dielectric constant of an interlayer insulating film, since this material has the smallest polarizability (see Non-Patent Document 1, for example).
In addition, a low density film, namely, a porous film has been studied to reduce the relative dielectric constant. The use of a porous film attracts attention as a method of achieving a relative dielectric constant of 2 or less.
The aforementioned interlayer insulating film with a low relative dielectric constant is manufactured by plasma CVD, spin coating or the like.
[Non-Patent Document 1] Nikkei Microdevices, Nikkei Business Publications, Inc., November 2004, pp. 58-65